(1) Field of the Invention
The present invention relates to a high water-absorptive resin emulsion in which high water-absorptive resin fine particles each having a diameter of 3 .mu.m or less are dispersed in an oil. Such a high water-absorptive resin emulsion can be prepared by a reversed phase emulsion polymerization of an ionic water-soluble monomer and a divinyl compound in an oil, and it can be utilized as an aromatic agent, a sealing material, a dew condensation inhibitor, a spreading agent for agricultural chemicals, and a cosmetic material.
(2) Description of the Prior Art
Heretofore, crosslinking polymers having ionic groups have been known as high water-absorptive resins. The most usual high water-absorptive resin is a crosslinked polyacrylate, and other resins of such a type include a cationic high water-absorptive resin disclosed in Japanese Patent Provisional Publication No. 154709/1983 and an amphoteric high water-absorptive resin in Japanese Patent Provisional Publication No. 154710/1983.
These conventional known high water-absorptive resins are in the form of particles each having a diameter of 100 .mu.m or more. Such powdery high water-absorptive resins are poor in workability, because they tend to raise a dust, are liable to condense owing to their high hygroscopicity, and are inconvenient for pipe transportation and metering due to not being a liquid.
These problems can be solved by providing a high water-absorptive resin emulsion in which high water-absorptive resin fine particles are dispersed in an oil, but such an emulsion has not been known before the filing of the present invention. The above high water-absorptive resin emulsion can be obtained by a reversed phase emulsion polymerization of a water-soluble monomer having an ionic group and a divinyl compound with an oil-soluble radical-generator. As a technique which is similar to the reversed phase emulsion polymerization, there is a reversed phase suspension polymerization. In the latter, a water-soluble radical-generator is used, and thus a polymerization will take place in an aqueous phase containing monomer, with the result that polymer particles each having relatively large diameters will be formed.
On the contrary, in the above mentioned reversed phase emulsion polymerization, the oil-soluble radical-generator is used, and in consequence the polymerization will occur in a micell, so that fine particles will be obtained.
The method for preparing the water-soluble polymer through the reversed phase emulsion polymerization is known, and its fundamental patent is U.S. Pat. No. 3284393. However, the polymer prepared according to the method of this U.S. Patent is water-soluble, since not having any crosslinking structure. Therefore, the polymer of the U.S. Patent is definitely different from that of the present invention in both chemical properties and applicable uses.
Further, in each of various ionic polymers which are known as ion exchange resins, a proportion of the crosslinking structure therein is about 10%, at the lowest and it shows no water swell characteristics.